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<p>Associates one or more exception handlers (catch-clauses) with a compound statement.
</p>
<table id="toc" class="toc"><tr><td>
<div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="try_catch.html%23Syntax"><span class="tocnumber">1</span> <span class="toctext">Syntax</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="try_catch.html%23Explanation"><span class="tocnumber">2</span> <span class="toctext">Explanation</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="try_catch.html%23Notes"><span class="tocnumber">3</span> <span class="toctext">Notes</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="try_catch.html%23Keywords"><span class="tocnumber">4</span> <span class="toctext">Keywords</span></a></li>
<li class="toclevel-1 tocsection-5"><a href="try_catch.html%23Example"><span class="tocnumber">5</span> <span class="toctext">Example</span></a></li>
</ul>
</td></tr></table>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Syntax">edit</a>]</span> <span class="mw-headline" id="Syntax">Syntax</span>
</h3>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td>
</tr>
<tr class="t-sdsc">
<td class="t-sdsc-nopad"> <code><b>try</b></code> <span class="t-spar">compound-statement</span> <span class="t-spar">handler-sequence</span>
</td>
<td class="t-sdsc-nopad">
</td>
<td class="t-sdsc-nopad">
</td>
</tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td>
</tr>
</table>
<p>where <span class="t-spar">handler-sequence</span> is a sequence of one or more <span class="t-spar">handler</span>s, which have the following syntax:
</p>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td>
</tr>
<tr class="t-sdsc">
<td> <code><b>catch</b></code> <code><b>(</b></code> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <span class="t-spar">type-specifier-seq</span> <span class="t-spar">declarator</span> <code><b>)</b></code> <span class="t-spar">compound-statement</span>
</td>
<td> (1)
</td>
<td class="t-sdsc-nopad">
</td>
</tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td>
</tr>
<tr class="t-sdsc">
<td> <code><b>catch</b></code> <code><b>(</b></code> <span class="t-spar">attr</span><span class="t-mark">(optional)</span> <span class="t-spar">type-specifier-seq</span> <span class="t-spar">abstract-declarator</span><span class="t-mark">(optional)</span> <code><b>)</b></code> <span class="t-spar">compound-statement</span>
</td>
<td> (2)
</td>
<td class="t-sdsc-nopad">
</td>
</tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td>
</tr>
<tr class="t-sdsc">
<td> <code><b>catch</b></code> <code><b>(</b></code> <code><b>...</b></code> <code><b>)</b></code> <span class="t-spar">compound-statement</span>
</td>
<td> (3)
</td>
<td class="t-sdsc-nopad">
</td>
</tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td>
</tr>
</table>
<table class="t-par-begin">


<tr class="t-par">
<td>  <span class="t-spar">compound-statement</span>
</td>
<td> -
</td>
<td>  the brace-enclosed <a href="statements.html%23Compound_statement" title="cpp/language/statements">sequence of statements</a> that constututes the body of a function
</td>
</tr>
<tr class="t-par">
<td>  <span class="t-spar">attr</span><span class="t-mark-rev t-since-cxx11">(C++11)</span>
</td>
<td> -
</td>
<td>  optional list of <a href="attributes.html" title="cpp/language/attributes">attributes</a>, applies to the formal parameter
</td>
</tr>
<tr class="t-par">
<td>  <span class="t-spar">type-specifier-seq</span>
</td>
<td> -
</td>
<td>  part of a formal parameter declaration, same as in a <a href="function.html" title="cpp/language/function">function</a> parameter list
</td>
</tr>
<tr class="t-par">
<td>  <span class="t-spar">declarator</span>
</td>
<td> -
</td>
<td>  part of a formal parameter declaration, same as in a <a href="function.html" title="cpp/language/function">function</a> parameter list
</td>
</tr>
<tr class="t-par">
<td>  <span class="t-spar">abstract-declarator</span>
</td>
<td> -
</td>
<td>  part of an unnamed formal parameter declaration, same as in <a href="function.html" title="cpp/language/function">function</a> parameter list
</td>
</tr>
</table>
<div class="t-li1">
<span class="t-li">1)</span> Catch-clause that declares a named formal parameter
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">try</span> <span class="br0">{</span> <span class="coMULTI">/* */</span> <span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> <a href="../error/exception.html"><span class="kw610">std::<span class="me2">exception</span></span></a><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span> <span class="coMULTI">/* */</span> <span class="br0">}</span></pre></div></div>
</div>
<div class="t-li1">
<span class="t-li">2)</span> Catch-clause that declares an unnamed parameter
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">try</span> <span class="br0">{</span> <span class="coMULTI">/* */</span> <span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> <a href="../error/exception.html"><span class="kw610">std::<span class="me2">exception</span></span></a><span class="sy3">&amp;</span><span class="br0">)</span> <span class="br0">{</span> <span class="coMULTI">/* */</span> <span class="br0">}</span></pre></div></div>
</div>
<div class="t-li1">
<span class="t-li">3)</span> Catch-all handler, which is activated for any exception
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">try</span> <span class="br0">{</span> <span class="coMULTI">/* */</span> <span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span> <span class="coMULTI">/* */</span> <span class="br0">}</span></pre></div></div>
</div>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Explanation">edit</a>]</span> <span class="mw-headline" id="Explanation">Explanation</span>
</h3>
<dl><dd>
<span style="font-size:0.7em; line-height:130%">See <a href="throw.html" title="cpp/language/throw"> throw exceptions</a> for more information about throw-expressions</span>
</dd></dl>
<p>A try-block is a <a href="statements.html" title="cpp/language/statements">statement</a>, and as such, can appear anywhere a statement can appear (that is, as one of the statements in a compound statement, including the function body compound statement). See <a href="function-try-block.html" title="cpp/language/function-try-block">function-try-block</a> for the try blocks around function bodies. The following description applies to both try-blocks and <a href="function-try-block.html" title="cpp/language/function-try-block">function-try-blocks</a>.
</p>
<p>The formal parameter of the catch clause (<span class="t-spar">type-specifier-seq</span> and <span class="t-spar">declarator</span> or <span class="t-spar">type-specifier-seq</span> and <span class="t-spar">abstract-declarator</span>) determines which types of exceptions cause this catch clause to be entered. It cannot be an <a href="reference.html" title="cpp/language/reference">rvalue reference type</a>, <a href="abstract_class.html" title="cpp/language/abstract class">abstract class</a>, <a href="incomplete_type.html" title="cpp/language/incomplete type" class="mw-redirect">incomplete type</a>, or pointer to incomplete type (except that pointers to (possibly <a href="cv.html" title="cpp/language/cv">cv</a>-qualified) <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span> are allowed). If the type of the formal parameter is array type or function type, it is treated as the corresponding pointer type (similar to <a href="function.html" title="cpp/language/function">function declration</a>)
</p>
<p>When an exception of type <code>E</code> is thrown by any statement in <span class="t-spar">compound-statement</span>, it is matched against the types of the formal parameters <code>T</code> of each catch-clause in <span class="t-spar">handler-seq</span>, in the order in which the catch clauses are listed. The exception is a match if any of the following is true:
</p>
<ul>
<li> <code>E</code> and <code>T</code> are the same type (ignoring top-level cv-qualifiers on <code>T</code>)
</li>
<li> <code>T</code> is an lvalue-reference to (possibly cv-qualified) <code>E</code>
</li>
<li> <code>T</code> is an unambiguous public base class of <code>E</code>
</li>
<li> <code>T</code> is a reference to an unambiguous public base class of <code>E</code>
</li>
<li> <code>T</code> is a (possibly cv-qualified) pointer <span class="t-rev-inl t-rev-inl-since-cxx14"><span>or a reference to a const pointer</span><span><span class="t-mark-rev t-since-cxx14">(since C++14)</span></span></span>, and <code>E</code> is also a pointer, which is implicitly convertible to T either by
</li>
</ul>
<dl><dd>
<ul>
<li> a standard <a href="implicit_cast.html" title="cpp/language/implicit cast">pointer conversion</a>
</li>
<li> a <a href="implicit_cast.html" title="cpp/language/implicit cast">qualification conversion</a>
</li>
</ul>
</dd></dl>
<ul><li> <code>T</code> is a pointer or a pointer to member <span class="t-rev-inl t-rev-inl-since-cxx14"><span>or a reference to a const pointer</span><span><span class="t-mark-rev t-since-cxx14">(since C++14)</span></span></span>, while <code>E</code> is <span class="t-lc"><a href="../types/nullptr_t.html" title="cpp/types/nullptr t">std::nullptr_t</a></span>.
</li></ul>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">try</span> <span class="br0">{</span>
  f<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> <a href="../error/overflow_error/overflow_error.html"><span class="kw618">std::<span class="me2">overflow_error</span></span></a><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
    <span class="co1">// this executes if f() throws std::overflow_error (same type rule)</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> <a href="../error/runtime_error/runtime_error.html"><span class="kw616">std::<span class="me2">runtime_error</span></span></a><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
    <span class="co1">// this executes if f() throws std::underflow_error (base class rule)</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> <a href="../error/exception.html"><span class="kw610">std::<span class="me2">exception</span></span></a><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
    <span class="co1">// this executes if f() throws std::logic_error (base class rule)</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span>
    <span class="co1">// this executes if f() throws std::string or int or any other unrelated type</span>
<span class="br0">}</span></pre></div></div>
<p>The catch-all clause <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span></span></span> matched exceptions of any type. If present, it has to be the last catch clause in the <span class="t-spar">handler-seq</span>. Catch-all block may be used to ensure that no uncaught exceptions can possibly escape from a function that offers  <a href="exceptions.html" title="cpp/language/exceptions">nothrow exception guarantee</a>.
</p>
<p>If no matches are found after all catch-clauses were examined, the exception propagation continues to the containing try-block, as described in <a href="throw.html" title="cpp/language/throw">throw-expression</a>. If there are no containing try-blocks left, <span class="t-lc"><a href="../error/terminate.html" title="cpp/error/terminate">std::terminate</a></span> is executed.
</p>
<p>When entering a catch clause, if its formal parameter is a base class of the exception type, it is <a href="copy_initialization.html" title="cpp/language/copy initialization">copy-initialized</a> from the base class subobject of the exception object. Otherwise, it is copy-initialized from the exception object (this copy is subject to <a href="copy_elision.html" title="cpp/language/copy elision">copy elision</a>).
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">try</span> <span class="br0">{</span>
   <a href="../string/basic_string.html"><span class="kw1045">std::<span class="me2">string</span></span></a><span class="br0">(</span><span class="st0">"abc"</span><span class="br0">)</span>.<span class="me1">substr</span><span class="br0">(</span><span class="nu0">10</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// throws std::length_error</span>
<span class="co1">// } catch( std::exception e ) { // copy-initialization from the std::exception base</span>
<span class="co1">//     std::cout &lt;&lt; e.what(); // information from length_error is lost</span>
<span class="co1">// }</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span> <span class="kw4">const</span> <a href="../error/exception.html"><span class="kw610">std::<span class="me2">exception</span></span></a><span class="sy3">&amp;</span> e <span class="br0">)</span> <span class="br0">{</span> <span class="co1">// reference to the base of a polymorphic object</span>
     <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> e.<span class="me1">what</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// information from length_error printed</span>
<span class="br0">}</span></pre></div></div>
<p>If the parameter of the catch-clase is a reference type, any changes made to it are reflected in the exception object, and can be observed by another handler if the exception is rethrown with <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">throw</span><span class="sy4">;</span></span></span>. If the parameter is not a reference, any changes made to it are are local and its lifetime ends when the handler exits.
</p>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx11">
<td>
Within a catch-clause, <span class="t-lc"><a href="../error/current_exception.html" title="cpp/error/current exception">std::current_exception</a></span> can be used to capture the exception in an <span class="t-lc"><a href="../error/exception_ptr.html" title="cpp/error/exception ptr">std::exception_ptr</a></span>, and <span class="t-lc"><a href="../error/nested_exception/throw_with_nested.html" title="cpp/error/nested exception/throw with nested" class="mw-redirect">std::throw_with_nested</a></span> may be used to build nested exceptions.</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td>
</tr>
</table>
<p>Other than by throwing or rethrowing the exception, the catch-clause after a regular try block (not <a href="function-try-block.html" title="cpp/language/function-try-block">function-try-block</a>) may be exited with a <a href="return.html" title="cpp/language/return">return</a>, <a href="continue.html" title="cpp/language/continue">continue</a>, <a href="break.html" title="cpp/language/break">break</a>, <a href="goto.html" title="cpp/language/goto">goto</a>, or by reaching the end of its <span class="t-spar">compound-statement</span>. In any case, this destroys the exception object (unless an instance of <span class="t-lc"><a href="../error/exception_ptr.html" title="cpp/error/exception ptr">std::exception_ptr</a></span> exists that refers to it).
</p>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Notes">edit</a>]</span> <span class="mw-headline" id="Notes">Notes</span>
</h3>
<p>The throw-expression <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">throw</span> <a href="../types/NULL.html"><span class="kw103">NULL</span></a><span class="sy4">;</span></span></span> is not matched by a pointer catch clause, because the exception object type is <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span></span></span>, but <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">throw</span> nullptr<span class="sy4">;</span></span></span> is matched by any pointer or pointer-to-member catch clause.
</p>
<p>If a catch-clause for a derived class is placed after the catch-clause for a base class, the derived catch-clause will never be executed.
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">try</span> <span class="br0">{</span>
   f<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> <a href="../error/exception.html"><span class="kw610">std::<span class="me2">exception</span></span></a><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
  <span class="co1">// will be executed if f() throws std::runtime_error</span>
<span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> <a href="../error/runtime_error/runtime_error.html"><span class="kw616">std::<span class="me2">runtime_error</span></span></a><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
  <span class="co1">// dead code!</span>
<span class="br0">}</span></pre></div></div>
<p>If <a href="goto.html" title="cpp/language/goto">goto</a> is used to exit a try-block and if any of the destructors of block-scoped automatic variables that are executed by the <code>goto</code> throw exceptions, those exceptions are caught by the try blocks in which the variables are defined:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1">label<span class="sy4">:</span> <span class="kw1">try</span> <span class="br0">{</span>
          T1 t1<span class="sy4">;</span>
          <span class="kw1">try</span> <span class="br0">{</span>
              T2 t2<span class="sy4">;</span>
              <span class="kw1">if</span><span class="br0">(</span>condition<span class="br0">)</span>
                  <span class="kw1">goto</span> label<span class="sy4">;</span> <span class="co1">// destroys t2, then destroys t1, then jumps to label</span>
           <span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span>  <span class="br0">}</span> <span class="co1">// catches the exception from the destructor of t2</span>
        <span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span>...<span class="br0">)</span> <span class="br0">{</span>  <span class="br0">}</span> <span class="co1">// catches the exception from the destructor of t1</span></pre></div></div>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Keywords">edit</a>]</span> <span class="mw-headline" id="Keywords">Keywords</span>
</h3>
<p><a href="../keyword/try.html" title="cpp/keyword/try"><tt>try</tt></a>,
<a href="../keyword/catch.html" title="cpp/keyword/catch"><tt>catch</tt></a>,
<a href="../keyword/throw.html" title="cpp/keyword/throw"><tt>throw</tt></a>
</p>
<h3>
<span class="editsection">[<a href="http%3A//en.cppreference.com/mwiki/index.php" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span>
</h3>
<div class="t-example">
<p> The following example demonstrates several usage cases of the <code>try-catch</code> block
 </p>
<div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;vector&gt;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw1">try</span> <span class="br0">{</span>
        <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"Throwing an integer exception...<span class="es1">\n</span>"</span><span class="sy4">;</span>
        <span class="kw1">throw</span> <span class="nu0">42</span><span class="sy4">;</span>
    <span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span> <span class="kw4">int</span> i <span class="br0">)</span> <span class="br0">{</span>
        <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">" the integer exception was caught, with value: "</span> <span class="sy1">&lt;&lt;</span> i <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
    <span class="br0">}</span>
 
    <span class="kw1">try</span> <span class="br0">{</span>
        <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"Creating a vector of size 5... <span class="es1">\n</span>"</span><span class="sy4">;</span>
        <a href="../container/vector.html"><span class="kw1067">std::<span class="me2">vector</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> v<span class="br0">(</span><span class="nu0">5</span><span class="br0">)</span><span class="sy4">;</span>
        <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"Accessing the 11th element of the vector...<span class="es1">\n</span>"</span><span class="sy4">;</span>
        <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> v.<span class="me1">at</span><span class="br0">(</span><span class="nu0">10</span><span class="br0">)</span><span class="sy4">;</span>  <span class="co1">// vector::at() throws std::out_of_range</span>
    <span class="br0">}</span> <span class="kw1">catch</span><span class="br0">(</span> <span class="kw4">const</span> <a href="../error/exception.html"><span class="kw610">std::<span class="me2">exception</span></span></a><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span> <span class="co1">// caught by reference to base</span>
        <a href="../io/basic_ostream.html"><span class="kw1439">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">" a standard exception was caught, with message '"</span>
                  <span class="sy1">&lt;&lt;</span> e.<span class="me1">what</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">"'<span class="es1">\n</span>"</span><span class="sy4">;</span>
    <span class="br0">}</span>
 
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">Throwing an integer exception...
 the integer exception was caught, with value: 42
Creating a vector of size 5...
Accessing the 11th element of the vector...
 a standard exception was caught, with message 'out_of_range'</pre></div></div> 
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